The present invention relates in general to an automated mechanism for optically inspecting cables, lines and the like.
The launch pads at Kennedy Space Center employ emergency egress systems in which slidewire cables and baskets are utilized to permit astronauts to descend quickly and safely away from the launch vehicle in case of an emergency. Periodic inspections of the cables are necessary to insure that failures have not occurred which could jeopardize safety. Cable failures are characterized by frayed or jammed strands, bird caging, stretching and corrosion. Inspection crews have been employed in the past to inspect the cables visually as they are lowered down the cables at a controlled speed in a slidewire basket. However, human application of tactile and visual senses in this manner limits the data obtained during the inspections to pass or fail indications. In addition, this operation is obviously hazardous, man intensive and time consuming. An alternative cable inspection technique that overcomes these drawbacks is therefore needed.
The present invention fulfills the foregoing need through provision of an automated cable and line inspection mechanism that visually scans the entire circumference of a cable or line as the mechanism travels along the length thereof without operator assistance. The mechanism includes a drive system, a video camera and a mirror assembly for providing the camera with a 360 degree view of the cable. These elements are mounted on a frame that can be attached to a cable or line to be inspected with drive and tension wheels in the drive system that engage the cable. An electric motor rotates the drive wheels, thereby driving the mechanism along the cable.
The mirror assembly includes first and second mirrors that are positioned facing portions of the cable that are facing away from the camera lens so that three parallel images of the cable are simultaneously supplied to the camera lens, each of which is of a different section of the cable. This enables the entire circumference of the cable to be imaged without rotational scanning of the camera around the cable.
Other sensing devices are also employed in the preferred embodiment. These include a laser micrometer that measures the diameter of the cable so that it may be determined whether the cable has stretched to an unacceptable degree. A position encoder is also employed to provide an indication of the position along the length of the cable where the cable image is being obtained at any given instant. This enables the location of any noted failures in the cable to be readily determined. Limit switches are also provided to sense when the mechanism has reached the far end of a cable or line, so that the drive motor can be reversed to send the mechanism back to its starting point, where the mechanism can be retrieved.
The video images generated by the video camera are combined with overlaid information, such as the cable diameter and position, and are stored in an on board video storage device, such as a VCR, for later review and analysis. In the preferred embodiment, the images are also transmitted with a video transmitter to a remote control station. In addition, an RF transceiver is employed to enable commands and other data to be communicated between a processor on the cable and line inspection mechanism and the remote control station.